KR20090094851A - Ballistic resistant sheet and ballistic resistant article - Google Patents

Abstract

The invention relates to a ballistic resistant sheet comprising a stack of at least 4 monolayers, each monolayer containing unidirectionally oriented reinforcing fibres with a tensile strength of between 3,5 an 4,5 GPa, and at most 20 mass% of a matrix material, the areal density of a monolayer is at least 25 g/m2 and with the fibre direction in each monolayer being rotated with respect to the fibre direction in an adjacent monolayer. The invention further relates to a ballistic resistant moulded article, i.e. a shaped part, comprising at least two ballistic resistant sheets according to the invention, which may be used as, for example, a panel for use in e.g. a vehicle, especially a curved panel, a hard insert e.g. for use in protective clothing and bullet resistant vests, etc. The ballistic resistant moulded article optionally may have a ceramic or a metal strike face. The ballistic resistant moulded article according to the invention offers protection against ballistic impacts such as bullets and ballistic fragments.

Description

Ballistic resistant sheet and ballistic resistant article {BALLISTIC RESISTANT SHEET AND BALLISTIC RESISTANT ARTICLE}

The present invention relates to ballistic resistant sheets and ballistic resistant articles.

The ballistic resistant sheet comprises at least four monolayers, each of which contains a reinforcing fiber oriented in a unidirectional direction with up to 20% by weight of matrix material, the fiber direction in each monolayer being rotated relative to the fiber direction in the adjacent monolayer. It includes a laminate of. Such ballistic resistant sheets are well suited for use in panels, in particular for crimped or molded ballistic resistant articles such as curved panels.

Such ballistic resistant sheets are known from US 4,623,574. This publication discloses the production of ballistic resistant sheets by cross-plying and laminating a plurality of monolayers each having a unidirectional oriented and extending chain polyethylene fiber and a matrix material and then pressing them into sheets. . Example 1 of this document refers to the production of a single layer by spirally wrapping polyethylene fibers side by side on a drum winder and coating the unidirectionally oriented fibers using a Kraton D1107 solution. . The plurality of monolayers thus obtained are laminated so that the fiber direction in the monolayer is perpendicular to the fiber direction in the adjacent monolayer. The resulting laminate was placed between parallel plates of an Apollo press and pressed for 5 minutes at a pressure of 0.6 MPa at a temperature of 130 ° C. and then cooled.

After a long study of improved ballistic resistant molded articles, the inventors have surprisingly found a ballistic resistant sheet that enables the production of a pressed panel or ballistic resistant molded article with surprisingly improved molding properties. Improved molding resistance means that a homogeneous product is obtained upon molding of a ballistic resistant article comprising several ballistic resistant sheets of the invention, in particular curved ballistic resistant articles, for example after molding It can be visually determined by the absence of a heterogeneous drape of the ballistic sheet.

According to the invention, each monolayer contains unidirectionally oriented reinforcing fibers having a tensile strength of 3.5 to 4.5 GPa and up to 20% by weight of matrix material, the monolayer has an area density of at least 25 g / m 2, each of An improved ballistic resistant sheet is provided that includes a stack of four or more monolayers in which the fiber direction in monolayer is rotated relative to the fiber direction in adjacent monolayers.

The ballistic resistant sheet according to the present invention provides excellent molding resistance.

This can be seen when a homogeneous molded article is obtained in the molding of a curved ballistic resistant article comprising several laminated ballistic resistant sheets of the invention without the irregular folding of the ballistic resistant sheet. A further advantage is that the ballistic resistant sheet according to the invention exhibits further improved ballistic performance.

As used herein, the term "monolayer" refers to a layer of matrix material that holds the fibers oriented together in a unidirectional orientation.

The ballistic resistant sheet comprises a stack of four or more monolayers, wherein the four or more monolayers are preferably connected or attached to each other. The monolayers are stacked in such a way that the fiber direction in each monolayer is rotated relative to the fiber direction in the adjacent monolayer. The rotation angle, meaning the smallest angle made by the fibers of the adjacent monolayers, is preferably between 0 ° and 90 °, more preferably between 10 ° and 80 °. Most preferably the angle is between 45 ° and 90 °.

The fibers in the ballistic resistant sheet of the present invention have a tensile strength of 3.5 to 4.5 GPa. The fibers preferably have a tensile strength of 3.6 to 4.3 GPa, more preferably 3.7 to 4.1 GPa, or most preferably 3.75 to 4.0 GPa.

The fibers can be inorganic or organic fibers. Examples of suitable inorganic fibers are glass fibers, carbon fibers and ceramic fibers.

Examples of suitable organic fibers having such high tensile strengths are aromatic polyamide fibers (often also called aramid fibers), in particular poly (p-phenylene terephthalamide), liquid crystal polymers and trapezoidal polymer fibers such as polybenzimidazole or polybenzoxazole , In particular poly (1,4-phenylene-2,6-benzobixazole) (PBO), or poly (2,6-diimidazo [4,5-b-4 ', 5'-e] pyridi Nylene-1,4- (2,5-dihydroxy) phenylene) (PIPD; also known as M5) and fibers of highly oriented polyolefin, polyvinyl alcohol and polyacrylonitrile obtained by, for example, a gel spinning process. . Preferably highly oriented polyolefin, aramid, PBO and PIPD fibers, or a combination of two or more thereof are used.

Even more preferably, high performance polyethylene fibers or highly stretched polyethylene fibers made of polyethylene filaments produced by gel spinning processes as disclosed, for example, in GB 2042414 A or WO 01/73173 are used. The advantage of these fibers is that they are lightweight and have very high tensile strength, making them particularly suitable for use in lightweight ballistic resistant articles.

Most preferably, multifilament yarns of ultra-high molecular weight linear polyethylene having an intrinsic viscosity of 5 dl / g are used.

The titer of a single filament of these fibers or yarns is preferably 2 denier or less, more preferably 1.9 denier or less. This results in excellent molding resistance of the ballistic resistant molded article comprising the ballistic resistant sheet. Most preferably the titer of a single filament of these fibers is 1.8 denier or less.

The term "matrix material" refers to a material that binds or fastens the fibers together and wraps the fibers as a whole or in part to maintain the structure of the monolayer during the handling and manufacture of the preformed sheet. The matrix material is in various forms and manners, for example, as a film between monolayers of fibers, as a transverse bonding strip between unidirectionally aligned fibers or as a transverse fiber (transverse to a unidirectional fiber), or It can be applied by impregnation and / or incorporation into the matrix material.

In a preferred embodiment, the matrix material is a polymeric matrix material and may be a thermoset material or a thermoplastic material, or a mixture of both. The elongation at break of the matrix material is preferably greater than the elongation of the fibers. The matrix material preferably has an elongation of 3 to 500%. In another preferred embodiment, the matrix material is preferably a polymeric matrix material having an elongation of at least 200%, more preferably from 300 to 1500%, even more preferably from 400 to 1200%. Among the group of thermosetting materials, vinyl esters, unsaturated polyesters, epoxies or phenolic resins are preferably selected as matrix materials. Among the thermoplastic material groups, preferably polyurethane, polyvinyl, polyacrylic, polyolefin or thermoplastic elastomer block copolymers such as polyisoprene-polyethylene-butylene-polystyrene or polystyrene-polyisoprene-polystyrene block copolymers are selected as matrix materials .

More preferably the matrix material in the process according to the invention has a 100% modulus of at least 3 MPa. This is understood as secant modulus measured according to ISO 527 at a strain of 100%.

Particularly suitably are matrix materials which can be applied as dispersions in water. Examples of suitable thermoplastic materials are acrylates, polyurethanes, modified polyolefins and ethylene vinyl acetate. Preferably, the matrix material contains polyurethane. More preferably, the polyurethane is a polyetherdiol-based polyetherurethane. This provides good performance over a wide temperature range. In a particular embodiment, the polyurethane or polyetherurethane is aliphatic diisocyanate based, which further improves product performance, in particular color stability.

Preferably the 100% modulus is at least 5 MPa. The 100% modulus is generally less than 500 MPa.

The amount of matrix material in the monolayer is 20% by weight or less. This results in a good combination of ballistic performance and molding. Preferably the amount of matrix material in the monolayer is at most 18.5% by weight, more preferably at most 17.5% by weight. This results in a better combination of ballistic performance and molding. Most preferably the amount of matrix material in the monolayer is 16% by weight or less. This results in the best combination of ballistic performance and molding properties of the ballistic resistant molded article.

It was found that the weight or area density of the monolayer should be at least 25 g / m 2 to achieve the desired molding. Preferably the weight of the monolayer is 30 to 200 g / m 2. More preferably, the weight of the monolayer is 30 to 180 g / m 2. Most preferably the weight of the monolayer is 40 to 150 g / m 2.

In the production of ballistic resistant sheets according to the invention, the unidirectionally oriented reinforcing fibers are applied, for example, by applying one or more plastic films to the top, bottom or both ends of the fiber side and then passing them through a heated press roll with the fibers. By impregnation with the matrix material. Preferably, however, the fibers are oriented in a parallel manner on one side and then coated with a predetermined amount of liquid material containing the matrix material. The advantage is that the fibers are impregnated faster and better. The liquid substance may be, for example, a solution, dispersion or melt of the plastic. If a solution or dispersion of the plastic is used to prepare the monolayer, the process also includes evaporating the solvent or dispersant. In this way a monolayer is obtained. The four or more monolayers are then laminated in such a way that the fiber direction in each monolayer is rotated relative to the fiber direction in the adjacent monolayer. Finally, the stacked monolayers are processed to be connected or attached to each other. A suitable treatment is to squeeze or laminate the laminate at sufficiently high temperatures. Higher temperatures will generally provide better adhesion. The adhesion can be further increased by applying some pressure. Suitable pressures and temperatures can be confirmed by some routine experimentation. In the case of high performance polyethylene fibers, the temperature may be 150 ° C. or less.

The ballistic resistant sheet according to the present invention may be appropriately laminated and pressed to form a ballistic resistant molded article. By ballistic resistant molded article is meant a molded article comprising two or more ballistic resistant sheets according to the invention, which are for example rigid panels for use in automotive panels, in particular curved panels, and protective garments and bulletproof vests, for example. Can be used. All of these articles provide protection against ballistic impacts such as bullets and ballistic debris.

The invention also relates to a ballistic resistant molded article comprising two or more ballistic resistant sheets according to the invention. In order for the ballistic resistant molded article to have excellent ballistic resistance, the number of ballistic resistant sheets in the article is 10 or more, more preferably 15 or more, and most preferably 20 or more.

In general, the thickness of the ballistic resistant molded article of the present invention is 125 mm or less, preferably 100 mm or less, more preferably 80 mm or less.

The ballistic resistant molded article according to the invention may be suitably combined with a ceramic layer and / or a metal layer. The metal and / or ceramic layer is then located on the ballistic resistant molded article side, ie striking face, towards the ballistic impact.

When the ballistic resistant molded article according to the invention is used in ballistic articles which may face the threat of ironclad bombs, the striking face is preferably a ceramic layer. In this way the article is obtained in a laminated structure, such as a ceramic layer / press laminated laminated ballistic resistant sheet. Optionally, a metal layer may be present as an additional layer between the ceramic layer and the compressively laminated ballistic resistant sheet.

Examples of suitable ceramic materials include alumina oxide, titanium oxide, silicon oxide, silicon carbide, silicon nitride and boron carbide. The thickness of the ceramic layer depends on the level of ballistic threat but generally varies between 2 mm and 30 mm. This composite article will preferably be positioned such that the ceramic layer faces the ballistic threat.

Suitable metals include aluminum, magnesium, titanium, copper, nickel, chromium, beryllium, iron and their alloys such as steel and stainless steel and alloys of aluminum and magnesium (so-called aluminum 5000 series), and aluminum, zinc and magnesium or zinc, Alloys with magnesium and copper (the so-called aluminum 7000 series).

The invention also relates to a method of making a ballistic resistant molded article. In this way the layered ballistic resistant sheet according to the invention can be suitably pressed at a pressure of more than 16.5 MPa in a press or press molding machine. Preferably the pressure is at least 20 MPa, or at least 25 MPa, as this further improves the ballistic resistance of the molded article. The temperature during the pressing is preferably 125 to 150 ° C. Higher temperatures have the advantage of further reducing the compression time, but should be maintained at a temperature of at least 10 ° C. below the temperature that starts to deteriorate the mechanical properties of the fiber. In the case of high performance polyethylene fibers, the temperature should be 150 ° C. or less, which is maintained below the melting range of the fibers. In a preferred embodiment, the laminate comprising the polyurethane matrix material is preferably pressed for at least 60 minutes at a temperature of 125 to 135 ° C. After the pressing at elevated temperature and before removing the press, the laminate is cooled to a temperature of less than 100 ° C, preferably less than 80 ° C. In a preferred embodiment the laminate is still cooled, preferably under pressure of at least 5 MPa, more preferably under pressure as in the preceding compaction step.

Finally, the present invention relates to a protective garment, such as a bulletproof vest, comprising the ballistic resistant molded article of the present invention in the form of a rigid panel.

Test methods referenced in the present invention are as follows :

IV: intrinsic viscosity is 135 ° C. in decalin according to PTC-179 (Hercules Inc. Rev. Apr. 29, 1982) method, dissolution time is 16 hours and 2 g / L solution amount of DBPC as antioxidant The viscosity measured at the concentration was determined by extrapolation to zero concentration.

Tensile Properties (measured at 25 ° C.): Tensile Strength (or Strength), Tensile Modulus (or Modulus) and Elongation at Break are ASTM D885M using a nominal gauge length of 500 mm of fiber, a crosshead speed of 50% / min. Determination was made for multiple filament yarns as specified in. The modulus was determined as the slope between strains of 0.3 to 1%, based on the measured stress-strain curves. For the calculation of the modulus and tenacity, the measured tensile force was divided by the titer determined by weighing 10 meters of the fiber, and the value in GPa was calculated considering the density as 0.97 g / cm 3. Tensile properties of the thin film were measured according to ISO 1184 (H).

The modulus of the matrix material was determined according to ISO 527. The 100% modulus was determined on a film strip having a length of 100 mm (free length between clamps) and a width of 24 mm. The 100% modulus is the secant modulus measured between 0% and 100% strain.

Hereinafter, the present invention is described in more detail by the following Examples and Comparative Experimental Examples, which are not limited to these.

Example  One

First, a unidirectional monolayer was prepared on a drum winder. Silicon treated paper was attached to the drum of the drum winder for this purpose. The drum was 160 cm in both circumference and width. Polyethylene yarns with a stiffness of 3.6 GPa and a titer of 1.92 denier / filament were wound on the drum winder with a pitch of 3.08 mm. The yarn was wetted with an aqueous dispersion of styrene isoprene styrene block copolymer before being wound onto the drum. By diluting the dispersion the amount of solid sucked by the yarn was adjusted to 18% by weight relative to the amount of yarn.

The drum was heated to about 65 ° C. to evaporate all the water. This produced a monolayer having a yarn area density of 48.6 g / m 2 and a matrix area density of 10.7 g / m 2.

Prior to adding the second monolayer, the first monolayer was removed from the drum, rotated 90 ° and attached to the drum again. Using the same procedure, a yarn was wound on the drum to attach a second monolayer to the first monolayer. The yarns of the second layer were oriented essentially perpendicular to the yarns of the first monolayer. This process was repeated to add the third and fourth monolayers.

The final sheet, ie the ballistic resistant sheet according to the invention, consisted of four monolayers oriented in the 0 ° / 90 ° / 0 ° / 90 ° direction. The area density (AD) was 237.4 g / m 2.

A total of 67 40 × 40 cm of the final sheets were laminated together and pressed into ballistic resistant panels.

The pressing conditions for obtaining the ballistic resistant panel are as follows:

The stack with the 67 final sheets was placed between two standard press platens. The temperature of the platen was 125 to 130 ° C. The package was held in the press until the center temperature of the package was between 115 and 125 ° C. The pressure was then increased to a compression pressure of 30 MPa and the package was held under the pressure for 65 minutes. The package was then cooled to a temperature of 60 ° C. at the same compression pressure.

The area density of the compacted panel was 15.9 kg / m 2. The area density of the yarns in the panel was 13 kg / m 2.

The obtained panel was subjected to a fire test according to the procedure set forth in STANAG 2920. A 7.62 × 39 mm mild steel core bullet, also known as an AK47 MSC bullet, was used. Bullets were obtained from Mesrs Sellier & Belliot, Czech Republic. These tests were performed for the purpose of determining V ₅₀ and / or absorbed energy. V ₅₀ is the speed at which 50% of the projectiles penetrate the armor plate. The test process is as follows. The first projectile was fired at V ₅₀ expected speed. The actual speed was measured just before the crash. When the projectile stopped, the next projectile fired at the intended speed about 10% higher. When penetrated, the next projectile fired at the intended speed about 10% lower. The actual impact velocity was always measured. V ₅₀ was the average of two highest stopping speeds and two lowest penetration speeds. The performance of the armor plate was also determined by calculating the kinetic energy of the projectile at V ₅₀ and dividing it by the AD of the plate (so called 'Eabs').

The V ₅₀ of the panel was found to be 782 m / s and the Eabs was 186 Jm 2 / kg.

compare Experimental Example  A

The sheet was prepared using the same procedure as described in Example 1 except that the yarn strength was 3.3 GPa, the titer was 3.3 denier / filament, the matrix content was 22%, and the yarn pitch was 6.08 mm. This formed a sheet in which each monolayer had four monolayers having a yarn area density of 24.3 g / m 2 and a matrix area density of 6.6 g / m 2.

Pressing 134 sheets yielded a panel with an area density of 16.7 kg / m 2 and yarn AD of 13.0 kg / m 2. The yarn AD was the same as the yarn AD in Example 1.

The V ₅₀ of the panel was found to be 666 m / s and the Eabs was 142 J m 2 / kg.

These results show that the panel according to the invention in Example 1 shows significantly higher Eabs, even though the amount of polyethylene fibers in the panel is equal to 13 kg / m 2.

Example 1 Comparative Experiment A Tensile Strength [GPa] 3.6 3.3 # Fault / sheet [-] 4 4 Wt% matrix 18 22 AD yarn / monolayer [g / m 2] 48.6 24.3 AD matrix / monolayer [g / ㎡] 10.7 6.9 AD monolayer [g / ㎡] 59.4 31.2 AD / sheet 237.4 124.9 # Sheet / Pack 67 134 AD pack [kg / ㎡] 15.9 16.7 Yarn AD in Pack [kg / ㎡] 13.0 13.0 V ₅₀ [m / s] 782 683 Eabs Jan 188 143

Claims (11)

Each monolayer contains unidirectionally oriented reinforcing fibers having a tensile strength of 3.5 to 4.5 GPa and up to 20% by weight of matrix material, wherein the monolayer has an area density of at least 25 g / m 2, and the fiber direction in each monolayer A ballistic resistant sheet comprising a laminate of four or more single layers that are rotated with respect to the fiber direction in the adjacent single layer. The method of claim 1, The ballistic resistant sheet whose area density of the said single layer is 40 g / m <2> or more. The method according to claim 1 or 2, The ballistic resistant sheet, wherein the monolayer comprises up to 18.5 weight percent matrix material. The method according to any one of claims 1 to 3, The ballistic resistant sheet, wherein the unidirectionally oriented reinforcing fibers have a tensile strength of 3.6 to 4.3 GPa. The method according to any one of claims 1 to 4, The ballistic resistant sheet, wherein the unidirectionally oriented reinforcing fibers are highly stretched polyethylene fibers. The method according to any one of claims 1 to 5, The ballistic resistant sheet, wherein the matrix material has a 100% modulus of at least 3 MPa. The method according to any one of claims 1 to 6, Ballistic resistant sheet, wherein the titer of a single filament is 2 denier or less. A ballistic resistant molded article comprising at least 10 ballistic resistant sheets according to any one of claims 1 to 6. The method of claim 8, The ballistic resistant molded article further comprising a ceramic or metal striking face. A protective garment, such as a bulletproof vest, comprising the ballistic resistant molded article of claim 8. Use of the ballistic resistant sheet according to any one of claims 1 to 7 in the manufacture of a ballistic resistant article.